| FLOYD HAYES |
| Hayes, F. E. 2001. Geographic variation in the Great Pampa-Finch Embernagra platensis complex: evidence for two species. Ardeola 50:223-235. Abstract.--Aims: The Great Pampa-Finch Embernagra platensis is represented by four subspecies belonging to two distinct groups occurring in allopatry: (1) nominate E. p. platensis in the east; and (2) E. p. olivascens, E. p. gossei and E. p. catamarcanus in the west. Morphological variation within the complex was assessed to infer the taxonomic relationship between the two forms. Location: Southern South America. Methods: Several size, plumage and soft part traits were measured for 339 specimens and analysed with univariate and multivariate statistical methods. Results: I found no evidence for long-distance migration, conflicting support for Bergmann's rule (body size negatively correlated with latitude and positively correlated with elevation), and more support for Gloger's rule. The structure and colouration of the bill were the most diagnostic traits. The absence of intermediate specimens and lack of clinal variation of bill colouration within each form demonstrates that intergradation either does not occur or is potentially restricted to a narrow, still undiscovered contact zone. Conclusions: Given the likelihood that bill structure and colour, combined with other traits, may represent reproductive isolating mechanisms between the two groups, I tentatively propose the recognition of two species within the E. platensis complex: the monotypic Great Pampa-Finch, E. platensis, and the polytypic Olive Pampa-Finch, E. olivascens. Resumen.--Objetivos: El Verd�n Embernagra platensis de Sudam�rica esta representado por cuatro subespecies que pertenecen a dos grupos distintos en alopatria: (1) la raza nominada E. p. platensis en el este; y (2) E. p. olivascens, E. p. gossei y E. p. catamarcanus en el oeste. Se estudi� la variaci�n geogr�fica para inferir la relaci�n taxon�mica entre los dos grupos. Localidad: El sur de Sudam�rica. M�todos: Algunas caracteristicas de tama�o, plumaje, y partes blandas fueron medidas para 339 especimenes y analizadas con m�todos estad�sticos univariables y multivariables. Resultados: No se encontr� evidencias de la existencia de migraci�n a largas distancias, ni evidencias para comprobar la ley de Bergmann (el tama�o del cuerpo est� correlacionado negativamente con latitud y positivamente con la elevaci�n), pero si se encontraron evidencias para comprobar la ley de Gloger. La estructura y coloraci�n del pico fueron las variables com mayor poder diagn�stico. La ausencia de especimenes intermedios y la ausencia de variaci�n clinal de la coloraci�n del pico en cada forma, demuestran que la gradaci�n no existe o potencialmente est� restringida a un �rea de contacto bien estrecho y no conocido. Conclusiones: Dado la probabilidad que la estructura y color del pico, combinado con otras caracteristicas, pueden representar mecanismos del aislamiento reproductivo entre los dos grupos, se propone tentativamente el reconocimiento de dos especies dentro del complejo de Embernagra platensis: el monot�pico Verd�n Grande, E. platensis, y el polit�pico Verd�n Olivo, E. olivascens. Key words.--Embernagra platensis, geographic variation, Great Pampa-Finch, morphological variation, South America, taxonomy |
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